The side length of an equilateral triangle is 20cm. How do you find the length of the altitude of the triangle?

2 Answers
Jul 9, 2018

Answer:

I tried this:

Explanation:

Consider the diagram:
enter image source here
we can use Pythgoras theorem applied to the blue triangle giving:

#h^2+10^2=20^2#

rearranging:

#h=sqrt(20^2-10^2)=sqrt(300)=17.3cm#

Jul 9, 2018

Answer:

#17.3cm#

Explanation:

You can use trigonometry to find the altitude (same as height) of the triangle.

In an equilateral triangle, all the sides are equal and all the angles are equal to #60°#

The altitude is the side opposite the #60°# angle

#o/20 = sin 60°#

#o = 20 xx sin60°#

#o = 17.3cm#